I appear to have found the problem. I deactivated PGP's auto wipe on delete option, reinstalled Avast a couple days ago, have done updates including today's, and all has been problem free. When I was using NAV, that PGP option gave me difficulty with some file deletions, leading me to think it might be a similar complication with Avast. BTW, AVG has no problem with that option.
I decided to try again after seeing how difficult it is with AVG to simply delete an email received in Pegasus that has the Netsky attached, and having seen how easy it was with Avast on my desktop. Since I receive that on a daily basis, the inconvenience was significant.
An issue with Avast, is that I can't do email scanning with it, since it won't allow me to send email out through my RoadRunner SMTP server as being from my mccune.cc email address. This is even when just setting it for incoming scanning.